A robust age model for the Cryogenian Pocatello Formation of southeastern Idaho (northwestern USA) from tandem in situ and isotope dilution U-Pb dating of volcanic tuffs and epiclastic detrital zircons

Abstract Tandem in situ and isotope dilution U-Pb analysis of zircons from pyroclastic volcanic rocks both glacial non-glacial sedimentary strata the Pocatello Formation (Idaho, northwestern USA) provides new age constraints on Cryogenian glaciation North American Cordillera. Two dacitic tuffs sampled within glacigenic lower diamictite interval Scout Mountain Member yield high-precision chemical abrasion zircon eruption depositional ages 696.43 ± 0.21 695.17 0.20 Ma. When supplemented by a detrital maximum ≤670 Ma for shoreface offshore sandstones unconformably overlying diamictite, these data are consistent with correlation to early (ca. 717–660 Ma) Sturtian glaciation. These 670–675 persist beds above upper cap dolostone units, up including purported “reworked fallout tuff,” which we instead conclude only ≤673 epiclastic detritus. Rare as young 658 provide units. This geochronological framework supports litho- chemostratigraphic correlations intervals (716–660 Marinoan (≤650–635 low-latitude glaciations, respectively. The thus contains more complete record glaciations than previously postulated.